Investigative Ophthalmology & Visual Science. 2008: 49(10); 4427-36 Associations between Aniosmetropia, Amblyopia, and Reduced Stereoacuity in a School-Aged Population with a High Prevalence of Astigmatism Velma Dobson, Hoseph M. Miller, Candice E. Clifford- Donaldson & Erin M. Harvey 2009. 4. 29 Ap. 박미라/ R4. 이경민

Previous Study/ Purpose Introduction

Introduction(1) Children who have anisometropia are known to be at risk of amblyopia. The greater the magnitude of the anisometropia, the more severe the amblyopia tends to be. Because anisometropic amblyopia is treatable in childhood, eye care professionals advocate methods for detection of anisometropia in young children.

Introduction(2) Problems of previous study Variability in the criteria used to define anisometropia Lack of data relating type & amount of anisometropia to presence of amblyopia Ignore the effect of cylinder anisometropia Ignore the effect of differences in cylinder axis between eyes

Introduction (3) Limitation Use of variety of VA chart Use of Titmus SA test : monocular & binocular cues Population relatively few cylinder anisometropia Failure to include pt. with cylinder anisometropia, interocular differences in cylinder axis>10° Glass effect Selection bias

Introduction(4) Purpose of this study To describe the relation between magnitude of anisometropia and interocular acuity difference, stereoacuity, and the presence of amblyopia in shcool-aged members with a high prevalence of astigmatism. Allows assessment of the role of astigmatism and astigmatic axis as risk factors for the development of amblyopia

Subjects/ Procedures/ Data analysis Methods

Subjects 1047 children 4 ~ 13 years of age Attended elementary school (kindergarten through 6th grade) on the society (about 5 schools were selected)

Procedure (1) : Eye exam Assessment of eye alignment : cover & uncover test at distance and near. Assessment of distance VA at 4m with ETDRS logMAR charts Measurement of refractive error 40 to 60 min. after instillation of one drop of proparacaine and 2 drops of cyclopentolate Estimate confirmed by retinoscopy Examination of external eye Fundus examination

Procedure (2) : VA & SA Eyeglasses VA : using ETDRS logMAR chart at 4m VA<20/20 in one or both eyes Hyperopia >2.5D on any merdian Myopia >0.75D on any merdian Astigmatism>1.0D in one or both eyes Anisometropia>1.5D SE VA : using ETDRS logMAR chart at 4m Rt eye: chart 1, Lt eye: chart 2 SA : using random dot test at 40cm

Data Analysis: Clincal notation 4 groups Isometropic (ISO) SE hyperopic anisometropia(SHA) SE myopic anisometropia(SMA) Cylinder anisometropia(CA)

Data Analysis: Vector notation Method of Thibos et al M(SE) J0(power in vertical/ horizontal merdian) 0.5D of J0= 1.0D of cylinder at 90° J45(power in oblique merdian) 0.5D of J45= 1.0D of cylinder at 45°

Fourier Approach of Thibos’ Spherical (S); Cylinder magnitude (C), Axis (α)  Spherical equivalent(M) + Jackson cross cylinder component Fourier analysis : complex waveform Sum of harmonically related sine waves and cosine waves, plus a constant Conversion from the polar Fourier form [M, Jxα] to the rectangular Fourier form [M,J0, J45] J0=J cos(2α), J45=J sin(2α) Conversion from the convention form to the rectangular Fourier form M=S+C/2 J0=C/2 cos2(β-90)=-C/2 cos2β, J0=C/2 sin2(β-90)=-C/2 sin2β Power Vectors : An Application of Fourier Analysis to the Description and Statistical Analysis of Refractive error Optometry & Visual Sciencs, 1997; 74(6): 367-75

Data Analysis: Vector notation Method of Harris Vector dioptric difference(VDD) Single No. representing the vector distance between 2 refractions. 1.41VDD= 1.0D SE difference without Dc. Minimal anisometropia group Interocular difference of <0.35VDD

Comparison with Harris’s notation Refractive error  Expression as matrix with Vector h (h1,h2, h3) Spherical (S); Cylinder magnitude (C), Axis (α) Mean & Variance calculation as matrix calculation. h1=S+C sin2α =M+J0 h2=-√2Csinαcosα = J45√2 h3= S+Ccos2α =M-J0 The mean and variance of samples of dioptric powers : the basic calculations Clinical & Experimental Optometry, 1990; 73: 89-92

Data Analysis ANOVA with post hoc analysis with Bonferroni correction VA & SA results as function of amount of anisometropia Χ2 analysis with post hoc analysis with Bonferroni correction Amblyopia prevalence as a function of amount of ansiometropia

Results Subject populations/ Anisometropia & Best corrected IAD Amblyopia/ Anisometropia & Best corrected SA Effect of previous glass wear Results

Results : Subject population Exclusion : 25 childeren  left sample of 972 Cataract, traumatic injury, strabismus, lid abnormlities, iris abnormalities, refused dilating drops, developmental delay, Hx of amblyopia, F/U loss Astigmatism ≥1D : 415 of 972 children(42.7%), ≥2D : 267 children(27.5%) Axis Rt. Eye : with the rule with ≥1D astigmatism in all 362 Lt. eye : with the rule with ≥1D astigmatism in 351 & against the rule in 1child. No oblique axis

Results : Anisometropia & BCIAD(1) Significant effect of amount of anisometropia in the SHA & CA group, but not in the SMA group. Within SHA groups: SE anisometropia ≥1.0D had significantly greater mean IAD than did in ISO group Within CA groups : Cylinder anisometropia≥3.0D had significantly greater mean IAD than did in ISO group

Results : Anisometropia & BCIAD(2) In Thibos’ method : no single group that different from the minimal anisometropia group in IAD In Harris’ method : significant effect of amount of anisometropia 1.41 ~2.12 VDD, 2.12~2.83VDD, ≥2.83VDD

Results : Amblyopia(1) Significant effect in amblyopia prevalence in the SHA & CA group, but not in the SMA group. Within SHA groups: SE anisometropia ≥1.0D had significantly greater amblyopia prevalence than did in ISO group Within CA groups : Cylinder anisometropia≥2.0D had significantly greater amblyopia prevalence than did in ISO group

Results : Amblyopia(2) In the whole groups, significant relation between prevalence of amblyopia & amount of anisometropia in both J0/J45 and VDD Post Hoc analysis In Thibos’ method : no single group higher than minial anisometropia In Harris’ method : higher than minimal anisometropia in 1.41 ~2.12 VDD, 2.12~2.83VDD, ≥2.83VDD

Results : Anisometropia & BCSA(1) SA: 48.6 arc sec. Significant effect of amount of anisometropia in the SHA, SMA & CA groups SHA group: SA worse in SE anisometropia ≥0.5D than minimal aniso. SMA group: SA worse in SE anisometropia ≥0.5D than minimal aniso. CA group : SA worse in SE anisometropia ≥0.5D than minimal aniso

Results : Anisometropia & BCSA(2) SA: 47.7 arc sec SA: 48.6 arc sec Significant effect of amount of anisometropia in both J0/J45 and VDD Post Hoc analysis In Thibos’ method : SA worse in J0/J45 anisometropia≥0.25D than ISO In Harris’ method : SA worse than minimal anisometropia in 0.71~1.41 VDD, 1.41 ~2.12 VDD, 2.12~2.83VDD, ≥2.83VDD

Results : Effect of previous glasses wear Responses on the parental questionnaire concerning previous glasses wear : 959 of 972 study (98.7%) Glasses wearing : reduce amblyopia in aniometropia patients. Similar to results for the entire group of children. Significant relation between the amount of anisometropia and the mean IAD in CA group & VDD termed calculation Significant relation between the amount of anisometropia and SA for all groups Significant relation between the amount of anisometropia and the prevalence of amblyopia in CA group and J0/J45 & VDD termed calculation

discussion

Discussion(1) Similarities with previous studies Nonastigmatic, hyperopic children with ≥1.0D of anisometropia showed significantly increased mean IAD Nonastigmatic, myoic children with ≥1.0D of anisometropia did not show significant increase in mean IAD The amount of anisometropia that resulted in decreased best corrected SA was identical with the amount of anisometropia that produced an increase in mean IAD & in prevalence of amblyopia

Discussion(2) Differences from previous studies In cylinder anisometropes Previous study : significant increase in IAD with >1.5D anisometropia This study : significant increase in IAD with >3.0D anisometropia Due to lower threshold for amblyopia Anisometropia using 2-vector based methods Include cylinder axis & magnitude both Thibos’ method : relate only to cylinder & axis anisometropia In Harris’ method : reflect anisometropia based on sphere, cylinder & axis value

Discussion(3) Strengths of this study Large, school-based study Population : high % of children with astigmatism Measurement of refractive errors CPR Retinomax autorefractor Retinoscopy BCVA measured by ETDRS chart Contains logMAR spacing of optotypes BCSA measured by random dot SA test Sample with no or minimal anisometropia Isometropic baseline data 1st large sample data relating vector-method calculation of anisometropia to data on IAD, SA & presence of amblyopia Include cylinder axis in calculations.

Discussion(4) Limitations of this study Many of the subjects with higher amounts of anisometropia had a Hx. Of spectacle wear Underestimated prevalence of amblyopia Overestimated the amount of anisometropia to produce amblyopia Differences in the variability of recognition acuity vs SA results Long examination time led to inattentiveness Absence of against-the-rule & oblique axis astigmatism in the subject population Relatively small No. Of subjects with myopic anisometropia ≥1.0D

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